Conventionally, techniques for detecting a motion region in a moving image have been widely used. An example of such techniques is a process carried out by an image processing device etc. for detecting a motion region where blurring is likely to appear and sharpening an image at the detected motion region, thereby improving the image quality of a moving image.
Patent Literature 1 discloses a technique relating to detection of a motion region. The technique is such that when noises exist on a transmission channel, characteristics of detection of a motion region are changed depending on the level of the noises so as to prevent wrong detection of a motion region.
With reference to FIG. 4, the following explains a circuit for detecting a motion region (hereinafter referred to as a conventional motion detection circuit) disclosed in Patent Literature 1. FIG. 4 is a block diagram showing a configuration of the conventional motion detection circuit. With the configuration shown in the drawing, the conventional motion detection circuit detects a motion region in a moving image with respect to each block region. The block region is a region consisting of one or a plurality of adjacent pixels.
As shown in the drawing, the conventional motion detection circuit includes a frame memory 910, a frame difference calculation section 920, an edge detection section 930, and a division section 960.
The frame memory 910 retains an input signal with respect to each frame, and outputs the retained signal with respect to each frame. Consequently, the signal outputted from the frame memory 910 indicates a frame immediately before the current frame.
The frame difference calculation section 920 calculates a frame difference between the current frame and a frame which is outputted from the frame memory 910 and which is immediately before the current frame. On the other hand, the edge detection section 930 detects, with respect to each block region, a high frequency component which is an edge component in the current frame.
Then, the division section 960 divides the frame difference calculated by the frame difference calculation section 920 by the absolute value of the high frequency component detected by the edge detection section 930, thereby obtaining a motion amount with respect to each block region.